Spray coating apparatus

ABSTRACT

Coating apparatus is disclosed which has a spray tip characteristic tailored to produce an atomized spray patter which is substantially triangular in cross section. This results in a coat distribution uniform particularly throughout a given width of a substrate. Means are also provided to hold the spray tip wide open for maintenance purposes.

1 Umted States Patent 1 1 [1 1 3,750,955 Nakai et a1. Aug. 7, 1973 SPRAY COATING APPARATUS 1.718.556 6/1929 Harrison 239/597 I 958,999 5/1910 Fordice 239/420 [75] 9 I 3,022,016 2/1962 Shrewsbury 239/597 Sameshlma, Fulmomlyai both of 3,341,354 9/1967 Woods et al 239/597 Japan 2,940,418 6/l960 Penrod et al. 239/597 [73] Assignee: Honshu Paper Company Limited,

Tokyo Japan Primary ExaminerLloyd L. King [22] Filed: June 23, 1972 Attorney-Bucknam & Archer [21] Appl. No.: 265,565

[30] Foreign Application Priority Data [57] ABSTRACT Sept. 10, 1971 Japan 46/6967] Coating apparatus is disclosed which has a spray tip [52] U.S. Cl. 239/420, 239/597 characteristic tailored to produce an atomized spray [51] Int. Cl. F23d 11/16, F23d 13/40, F23d 15/00 patter which is substantially triangular in cross section. [58] Field of Search 239/413, 420, 421, This results in a coat distribution uniform particularly 239/426, 597 X, 41 1 throughout a given width of a substrate. Means are also provided to hold the spray tip wide open for mainte- [56] References Cited nance purposes.

UNITED STATES PATENTS 1,791,854 2/1931 Strin 239/420 6 Claims, 3 Drawing Figures PAIENTEU 3. 750.955

sum 2 a; 2

FIG.2

SPRAY COATING APPARATUS This invention relates to apparatus for applying solutions or dispersions of various coating materials onto the surface of a substrate, more particularly to spray coating apparatus for depositing a uniform film of coat on sheet structures.

The coating materials to be handled by the apparatus of the invention are hereinafter referred to simply as coating liquid which collectively includes water solutions or dispersions such as of aqueous adhesives, hot melt adhesives, water-soluble paints, organic and inorganic solvents, water-repellent agents, surfactants and the like.

Spray guns of various types are known for use in coat or paint application. A typical example is an air spray gun designed to mix a coating liquid with a strong blast of air either within the tip of the spray nozzle or at a point immediately outside of the spray tip, thereby atomizing the liquid for deposition on a desired surface. While these spray guns are extensively used in paint application for their case of handling, they have certain limitations and difficulties in their performance. Firstly, the quantities of coating liquid the spray gun can handle are extremely limited, and to increase its spray ca pacity will literally require increased number of spray nozzles. Secondly, the patterns of coat produced by the spray gun having a cross-sectionally round tip are necessarily circular with adjacent dots of coat overlapped so that it is difficult to obtain a coat of uniform thickness throughout the entire surface of a substrate. Thirdly, owing to limited spray capacity and circular spray tip characteristic of the spray gun, it is difficult to provide a coat distribution on a relatively wide sheet substrate with any degree of uniformity widthwise of the substrate.

Whereas, it is an object of the present invention to provide a novel apparatus for applying a coating liquid onto a substrate which has increased capacity and a performance characteristic to permit a uniform distribution of coat.

It is another object of the invention to provide an air spray coating apparatus which will eliminate the abovenoted difficulties of the conventional air spray guns and which can produce a coat distribution substantially uniform throughout a given width of a substrate.

It is a further object of the invention to provide an air spray coating apparatus which includes means for holding the spray tip wide open for maintenance purposes.

These and other objects and features of this invention will appear clear from the following detailed description of a preferred embodiment of the invention taken in conjunction with the accompanying drawings in which: 1

FIG. 1 is a sectional view of an important part of the apparatus of the invention;

FIG. 2 is a front elevation of the apparatus of FIG. 1; and

FIG. 3 is a schematic illustration utilized to explain a spray pattern of coat produced by the apparatus of the invention. Like numerals refer to like parts throughout the di'awings.

According to the present invention, there is provided a spray coating apparatus which essentially comprises a cylindrical air header receiving a supply of compressed air and having a plurality of downwardly di rected openings, at first and a second lip member extending substantially to full length of said cylindrical air header and secured at one ends thereof to said header, said first and second lip members defining therebetween an air chamber communicating with said openings of the header and converging at the other or free ends, thus forming thereatan air jet slit for discharging compressed air, a block member disposed in opposed relation to the outer wall of said first lip member and defining therewith a liquid chamber, a blade secured at one end to said block member and having the other end in abutting relation to the free end of said first lip member for forming therebetween a spray tip, and a plurality of liquid supply tubes secured to said block member and supplying a coating liquid to said liquid chamber.

Referring now to the drawings and FIG. 1 in particular, there is shown a coating machine embodying the invention for applying an atomized coat over the surface of a relatively wide sheet substrate.

This machine comprises a cylindrical air header 101 horizontally mounted on a suitable frame (not shown) for receiving a supply of air compressed for example to a water column of between 2,000 mm and 3,000 mm. The header 101 is provided at a lowerpart with a series of openings 102 aligned in the axial direction of the header and each having a diameter of about 50 mm and spaced about 65 mm apart from each other. The openings 102 are directed downwardly towards and comm u? nicating with an air chamber later described There is provided a pair of lip members 103 and 104 extending substantially to full length of the cylinder air header 101 and defining therebetween an air chamber 105 which is substantially triangular in cross section and converges into an air jet slit 106 about 0.25 to 0.35 mm wide. The first or upper lip member 103 extends vertical with respect to the axis of the header 101 and has its upper end portion secured by bolts 107 through a washer 108 to the peripheral wall of the header 101. The lower inner wall 109 of the upper lip 103 is reduced gradually towards the slit 106. The lower lip member 104 is disposed at aprede'termined angle with respect to the upper vertical lip member 103 and secured in place by a lip holder 110. More specifically, the lower lip 104 has its upper end secured by bolts 111 to one end of the holder which in turn is secured at the other end by bolts 112 to the bottom part of the cylindrical header 101. A positioning bar 113 is adapted to set the lip holder 110 in the proper position.

The reference numeral 114 designates set screws which are adapted together with the bolts 112 to coarsely adjust the air slit or gap 106. For fine adjustment of this gap, there are provided set screws 115 adjacent to the bolts 111.

There is shown a block member 116 of a triangular cross section having a vertical inner wall 11'! disposed in opposed relation to the outer wall 118 of the vertical lip 103 so as to define therebetween a liquid chamber 119 for accumulating therein a predetermined level of a coating liquid C. The block 116 has an inclined outer wall 120 and a longitudinal recess 121 substantially parallel thereto for receiving a pair of blade holders 122 and 123 that are secured by bolted keep plate 124 to the outer wall 120 of the block 116. The blade holders 122 and 123 are adapted to hold therebetween a spray tip forming blade 125 of small thickness in a position wherein the edge of this blade isheld in end-to-end abutting relation to the pointed tip of the vertical lip 103 thereby forming a spray tip 126. Altematively, the tip end of the blade 125 may be spaced minutely apart from the tip of the vertical lip 103 where increased rate of spray is desired, for which purpose there is provided a set screw 143 thereby adjusting the gap between the edge of the blade 125 and the tip of the vertical lip 103. Also alternatively, the edge of the blade 125 may be recessed to provide a plurality of depressions 144 through which the coating liquid is allowed to flow out as seen in FIG. 2. These depressions 144 may be preferably about 2mm wide and about 0.8mm deep and spaced by a pitch of about 8mm.

There are provided a pluralityjof liquid supply tubes 127 each having one end inserted through the block 116 and the other end connected to a liquid supply hose (not shown). An overflow baffle 128 is secured to the vertical inner wall 117 of the block member 116. This baffle is adapted to prevent localized flow of the liquid directly from the tubes 127 into the liquid chamber 119 which would otherwise cause irregularities in the spray of liquid at the tip 126 and hence in the thickness of coat on the substrate. The baffle 128 is thus provided for allowing the liquid to overflow the same and thereby fall uniformly into the liquid chamber.

In a preferred form of the invention, means are provided for moving the liquid chamber forming block 1 16 away from the vertical lip 103 to hold the spray tip 126 wide open so as to facilitate the removal of any foreign matters or coagulated residual liquid from the spray tip 126 and also the cleaning of interior parts of the spray system. Also advantageously, the block 116 may be thus held in a fully open, inoperative position during downtime of the machine thereby eliminating the deposition of undesirable coagulated materials on the blade 125 or on the outer wall 118 of the vertical lip 103.

The means for holding the block 116 movable comprises an air cylinder 129 having a flange 130 pivotally connected by pin 131 to a support arm 132 secured to the upper end of the vertical lip 103, a piston rod 133 operatively associated with the air cylinder 129 and having a flanged end 134, a first bracket member 135 secured by bolts 136 to the block member 116 and having a horizontal arm 137 pivotally connected to the flanged end 134 of the piston rod 133 and a vertical arm 138 pivotally connected by pin 139 to a horizontal lug 140 extending from a second bracket member 141 secured by bolts 142 to the outer wall 118 of the vertical lip 103. With this arrangement, the upward stroke of the piston rod 133 rotates the first bracket member 135, hence the block member 116 clockwise to hold the spray tip 126 wide open.

It will be understood that there is provided, although not shown, at the other end of the machine or at the left-hand side of FIG. 2, an additional air cylinder and piston arrangement of the above description.

With this construction, the coating apparatus according to the invention will be set in the operative position which is substantially perpendicular to the direction of travel of a substrate to be coated. For purposes of illustration, the substrate is shown to be a sheet of nonwoven web S in FIG. 3. Air compressed to about a water column of 2,000 mm is supplied axially of the air header 101 and flows through openings 102 for jetting from the air slit 106. In the event the slit 106 is found locally wider or narrower than desired due to the fact that the lower lip member 104 and its holder 110 are relatively wide, such irregularities in the opening of the slit 106 may be corrected by fine adjustment of bolts 111 and set screws 115.

A coating liquid C is supplied from the hoses (not shown) through the supply tubes 127 and flows over the baffle 128 into the liquid chamber 119, until a predetermined level of this liquid is established and maintained. The liquid is fed by suction and atomized at a point just outside the spray tip 126 by a stream of air blown from the jet slit 106. The liquid thus atomized forms a cross-sectionally triangular spray pattern as seen in FIG. 3, which pattern is attributed to the peculiar characteristic of the spray tip 126 which extends linearly widthwise of the machine in association with the air jet slit 106. Where large quantities of coating liquid are to be applied, the gap in the spray tip 126 or the number of depressions 144 in the blade 125 may be increased with proportionate increases in the feed of liquid C to the liquid chamber 119. At the same time, adjustment of the velocity and pressure ofjet air in the air chamber provides a spray coat of controlled particle size.

Having thus described the invention, it will be understood that various changes and modifications may be made in the specific fonn and construction herein advanced, without departing from the scope of the appended claims.

What is claimed is: I

l. A spray coating apparatus which comprises a cylindrical air header receiving a supply of compressed air and having a plurality of downwardly directed open ings, a first and a second lip member extending substantially to full length of said cylindrical air header and secured at one end thereof to said header, said first and second lip members defining therebetween an air chamber communicating with said openings of the header and converging at the other or free ends, thus forming thereat an air jet slit for discharging compressed air, a block member disposed in opposed relation to the outer wall of said first lip member and defining therewith a liquid chamber, a blade secured at one end to said block member and having the other end in abutting relation to the free end of said first lip member for forming therebetween a spray tip, and a plurality of liquid supply tubes secured to said block member and supplying a coating liquid to said liquid chamber.

2. A spray coating apparatus as defined in claim 1 wherein said second lip member is provided with set screws for adjusting the opening of the air slit.

3. A spray coating apparatus as defined in claim 1 wherein said block member is provided with an overflow baffie extending lengthwise of said first lip member for maintaining a uniform flow of liquid on entry to said liquid chamber.

4. A spray coating apparatus as defined in claim 1 wherein said blade is provided along its longitudinal edge with recesses or depressions.

5. A spray coating apparatus which comprises a cylindrical air header receiving a supply of compressed air and having a plurality of downwardly directed oen ings, a first and a second lip member extending substantially to full length of said cylindrical air header and secured at one ends thereof to said header, said first and second lip members defining therebetween an air chamber communicating with said openings of the header and converging at the other or free ends, thus forming thereat an air jet slit for discharging compressed air, a block member disposed in opposed relation to the outer wall of said first lip member and defining therewith a liquid chamber, a blade secured at one 6. A spray coating apparatus as defined in claim 5 wherein said means comprises an air cylinder, a piston rod operatively associated therewith, a bracket member secured at one end to said block member and pivotally connected at the other end to said piston rod. 

1. A spray coating apparatus which comprises a cylindrical air header receiving a supply of compressed air and having a plurality of downwardly directed openings, a first and a second lip member extending substantially to full length of said cylindrical air header and secured at one end thereof to said header, said first and second lip members defining therebetween an air chamber communicating with said openings of the header and converging at the other or free ends, thus forming thereat an air jet slit for discharging compressed air, a block member disposed in opposed relation to the outer wall of said first lip member and defining therewith a liquid chamber, a blade secured at one end to said block member and having the other end in abutting relation to the free end of said first lip member for forming therebetween a spray tip, and a plurality of liquid supply tubes secured to said block member and supplying a coating liquid to said liquid chamber.
 2. A spray coating apparatus as defined in claim 1 wherein said second lip member is provided with set screws for adjusting the opening of the air slit.
 3. A spray coating apparatus as defined in claim 1 wherein said block member is provided with an overflow baffle extending lengthwise of said first lip member for maintaining a uniform flow of liquid on entry to said liquid chamber.
 4. A spray coating apparatus as defined in claim 1 wherein said blade is provided along its longitudinal edge with recesses or depressions.
 5. A spray coating apparatus which comprises a cylindrical air header receiving a supply of compressed air and having a plurality of downwardly directed oenings, a first and a second lip member extending substantially to full length of said cylindrical air header and secured at one ends thereof to said header, said first and second lip members defining therebetween an air chamber communicating with said openings of the header and converging at the other or free ends, thus forming thereat an air jet slit for discharging compressed air, a block member disposed in opposed relation to the outer wall of said first lip member and defining therewith a liquid chamber, a blade secured at one end to said block member and having the other end in abutting relation to the free end of said first lip member for forming therebetween a spray tip, a plurality of liquid supply tubes secured to said block member and supplying a coating liquid to said liquid chamber, and means for moving said block member towards and away from said first lip member.
 6. A spray coating apparatus as defined in claim 5 wherein said means comprises an air cylinder, a piston rod operatively associated therewith, a bracket member secured at one end to said block member and pivotally connected at the other end to said piston rod. 